Practical Applications
by Dierdre
Summary: Sam tests out a new invention. Ratchet is not amused.


_**AN:** It's been nearly a year since I wrote a fanfic, so I'm really hoping this doesn't suck._

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Samuel James Witwicky --hero of Mission City, slayer of Megatron and official interspecies diplomat-- folded his hands behind his head and fought the urge to sulk.

He was lying in the middle of an Autobot-sized examination table, feeling like a fleshy island in a sea of glass smooth metal, his shirt a crumpled islet at his side. The bright halogen lights above him were blocked by a familiar boxy form, and his skin crawled and itched like ants swarming under his skin. It was a scenario that had become routine in the past month, which was just another example of the incredibly weird turn his life had taken.

"Look," Sam said, his voice heavy with resignation. "I appreciate this whole Hippocratic Oath thing you've got going on, but this is the second examination you've given me this week. You ever heard of overkill?"

The figure above him turned and shifted, sending layered shadows flickering over his form like clouds beneath the sun, before it pulled away entirely. He squinted against the intruding light, watching as a person marginally smaller than a two story building moved with oiled grace, his optics shifting from electric blue to a brilliant, neon green. The insectile crawl beneath Sam's skin changed accordingly; the ants switching from a swim through his veins to a double-time march over every bone. Light glinted off a curved helmet as Sam fought not to writhe, and the young man thought uncharitably that the mech's chartreuse paintjob gave him the appearance of a seasick lemon.

"The only oaths I've taken are the ones I made to myself," Ratchet replied. His face was serene with the effort of concentration, his processors absorbing terabytes of anatomical information per second. "And your skin is still healing. These visits are necessary to monitor your recovery."

"I get that, Ratchet. It's the _number_ of visits I object to. I swear, I'm so out of the woods now, I'm in the suburbs." He scratched at the scar tissue spider-webbing over his belly, grimacing at the lingering tenderness of the new skin. "All that's left is the itchy and bitchy stage."

"What a delightful turn of phrase," the medic said dryly. With rock steady hands and infinite delicacy, he pulled Sam's probing fingers away from the fragile tissue. "I know you dislike the scanner probes, but to use another English idiom: suck it up. I'm almost finished."

"Fine. Just as long as you know you're perpetuating negative alien stereotypes."

"Thanks _so_ _much_ for the warning, Samuel. Now hold still. I need to take a few measurements."

Sam sighed in relief as Ratchet shut off the scanner probes and switched to a pale red light, which passed over his body with blessedly little sensation. "Measurements? That's new."

"Indeed. You may get up now, if you wish." Ratchet's optics cycled back to their normal hue as the red light winked out of existence, announcing the end of Sam's torture session. He was quick to rise to his feet and pull the shirt over his head, absentmindedly tugging the hem away from his body. Bandages were no longer required to protect the wounds, but it would be a while before the scars desensitized.

The medical bay was so cavernous that Ratchet's footsteps echoed dully when he moved away from the examination table, bound for a nearby desk. Instruments longer than Sam was tall cluttered its top in a state of organized chaos, effectively blocking Sam's view as Ratchet peered critically at an unseen project. His optics narrowed in thought, and a moment later a tiny clamp telescoped from his left index finger.

As the mech leaned over and began to tinker busily, Sam sat down on the edge of the table, fearlessly letting his legs dangle over the brink. Curiosity was poking at him with a sharp stick, but he knew by now that it was useless to pry information out of Ratchet until he was good and ready.

Fortunately for him and his impatient nature, Sam didn't have to wait long. There was a muttered Cybertronian curse that Sam had come to recognize, followed by an irritable question in English. "Why do you organics have to be so fragging small?"

"To make it harder for you robots to get a target lock," Sam said brightly, sensing an end to his boredom. "Want to tell me what you're working on?"

"Something that should keep _that_ from happening again." Ratchet stabbed a finger in the general direction of Sam's gut, before continuing with grudging honesty, "Not as easily, at least."

Sam ran a hand over his stomach, feeling his shirt scrape like fine sandpaper over the new scars; souvenirs from a heavily damaged and extremely pissed off Ravage. "Cool. I already got enough scars to impress the ladies."

"I'm sure Mikaela and Bumblebee agree with you on that." The tiny clamp slid seamlessly back into his index finger, and when he walked back over to Sam a moment later, there was a human-sized harness resting like a toy in the cup of his palm. "Keep in mind that this is just a prototype, Samuel. Provided it works, I'll have Mikaela help me convert it into something a little less obtrusive."

Sam pulled the contraption from Ratchet's hand, where it tumbled onto his lap in a tangle of vinyl straps. The main body of the thing was reminiscent of football shoulder pads, with a thin, wire-laced backpack that could only contain a battery.

"This is great, Ratchet!" Sam lifted it up and tested its weight, before quirking an eyebrow at the medic. "What is it?"

"It's a miniaturized version of our own intradermal PEX shields, which I've modified to work outside the body." Noticing the look of polite incomprehension on Sam's face, the mech vented a humanlike sigh. "It's a portable force field."

"What, like in Star Trek?" He looked down at the harness with new appreciation; a wide, delighted grin slowly spreading over his face. "You're the most awesome medic in existence."

With the air of one acknowledging a simple truth, Ratchet nodded once. Sam was quick to stand and struggle into the harness, easily adjusting the black straps crisscrossing over his chest. The single strap spanning his back was more difficult to reach, however, and after an amusing moment watching the human contort himself, Ratchet came to his aid. The clamp extended from his finger once again, and he used it to grip the strap and tighten it with exquisite precision.

With the portable shield fastened securely around the human's torso, Ratchet pinged him with a quick scanner probe. Sam, using the tabletop as a makeshift mirror, was so busy posing in his new harness that he barely noticed. "A later version of this model will be made of a more breathable material and streamlined to fit readily under clothing, like one of your law enforcements' Kevlar vests."

Sam shrugged dismissively, although the gesture was somewhat ruined by the dark blue pads binding his shoulders. "I don't mind looking like a jock for a while, as long as it keeps me from getting squished."

Ratchet's engine thrummed in agreement, and he indicated a button on the harness, which was deeply imbedded in one of the stiff shoulder pads. Marveling at the skill it had taken for such a large mech to create something so small, Sam pushed the button until he heard a click. There was no discernable change, except for a hum that was more felt than heard. It tingled up the back of his neck and itched the inside of his ears, making him shiver involuntarily.

"So how does it work?"

"It's a field that hovers approximately a centimeter above your skin, conforming seamlessly over your flesh and clothing. It lies outside your visible spectrum, although it can be viewed with Cybertronian optics. Like so." There was a distinctive pulse of sound as Ratchet's holographic emitter flared to life, projecting a pale blue radiance over Sam's skin. It shimmered and writhed like oil over a choppy sea, and Sam whistled in appreciation.

Allowing the hologram to gutter out of existence, Ratchet continued, " A rather simplistic AI program uses the formula one half times the weight in kilograms times velocity in meters per second squared to measure the kinetic energy of an incoming object and to repel any that register above a certain joule. "

Sam blinked, and then nodded slowly. "So… magic. Got it."

Even without the necessary tendons, Ratchet still gave the impression of rolling his eyes. "Let me explain in a different way. The formula is the measurement for kinetic energy, which applies to any moving object. Since the primary reasons for damage to a structure, living or otherwise, is directly related to the mass and speed of a projectile, it's a good way to measure the probable damage caused by said projectile. I've done an extensive amount of research to ascertain the onset of damage to the average human body, which is approximately sixty-five joules.

"Using this as a baseline, I've calibrated the AI so that objects of a low enough speed and/or density will pass right through the shield. For example…" He pulled out one of the polishing rags he kept stashed on his person and tossed the square of white microfiber, which settled over Sam like a heavy bed sheet.

The young man squawked in surprise and flailed like an indignant ghost, before pulling the cloth away from his head and glaring at Ratchet through a veil of tousled hair. Ratchet, unrepentant, merely grinned. "This will allow you to interact with and manipulate most objects that you would ordinarily encounter in your day, without triggering the shield."

Retrieving the rag and stuffing it in a compartment beneath his chestplate, Ratchet then reached out and gently gripped Sam's arm between thumb and forefinger. He pulled it away from the young man's body, the limb looking like a toothpick in his grip. "If something were to hit the shield at a great enough mass and velocity, however-" Without warning, Ratchet rapped a knuckle against Sam's forearm with a force that should have fractured bone. Instead there was a brief flash of pale blue, and the medic's finger jerked back as if pushed. "Then the AI is triggered, instantly reflecting most of the energy out and away from your body. It creates a rather interesting ricochet effect."

Sam jerked his arm out of Ratchet's grip, his face slightly pale as he flexed his fingers experimentally.

"Thanks for the demo, Ratch," he said tightly, "but warn a guy next time." Ratchet shrugged in apology, and Sam seemed to regain his equilibrium. "So all I need is a jetpack attachment, and I'm the next Superman."

"Hardly. This shield is of an admittedly brilliant design, but it can only deflect 99 percent of an object's kinetic energy. If an object is large and/or fast enough, it will still transfer some of that energy to you."

Sam nodded at that. "That explains it, then. I thought I felt something when you hit me. Really light, like a fly landing on my arm."

"Exactly. That was the one percent the shield could not deflect." The mech drummed his fingers against the table with a sound like gunfire, his expression momentarily distant. "Let me put it into perspective for you. If Will were to punch you in the back, the only way you'd know would be when you heard his fingers break. Being shot with a .30 caliber weapon would feel like a slap, while a terminal velocity fall would probably end in bruising and a concussion. Prowl running over you at fifty miles an hour would mean a broken bone or three, while an encounter with Prime at the same speed would cause extensive internal damage. A direct hit from an AIM 120 missile would liquefy you inside your shield, and getting stomped on by Superion would leave nothing but a greasy stain.

"Do you understand what I'm telling you, Samuel?" He reached out and lightly tapped the harness's battery pack, his expression as inflexible as granite. "This little gizmo makes you less fragile, but it doesn't give you the powers of a fictional comic book character. You can still be hurt. You can still be killed. Am I being clear?"

"Crystal, Ratchet. I still got a lot of screaming and running in my future." A shadow of some darker emotion passed over Sam's features, before he looked up at Ratchet and forced lightness into his tone. "I take it you're going to make duplicates for the rest of the high-risk squishables? 'Kaela, Will, Robbie and their squad?"

"Glenn and Maggie, too, if they keep insisting on finding trouble." Turning away from Sam, he began fastidiously straightening the tools at his desk and packing up the redundant systems for the force field. "It will be a while before that happens, though. I need to perform a wide spectrum of tests to expose any possible glitches in the system."

"Well, if it helps, I'll gladly be your guinea pig." There was a long, contemplative pause, and then Sam asked, "So this shield would protect me from a fall of, say, twelve feet?"

"Certainly," Ratchet replied, not looking up from his task. "A drop of 3.66 meters would take less than a second and would only-"

"_Geronimo!_"

Ratchet whipped around at the unexpected shout, just in time to see Sam leap from the exam table like a kamikaze lemming, spread-eagled and destined for an impressive concrete belly flop. The mech darted forward with a strangled rev of his engine, his hands outstretched, just as Sam hit the ground in a flash of palest blue. The shield forced him back into the air with a literal bounce, his limbs flailing in a rag doll rebound. Ratchet caught him an instant later, all but enveloping the human in a cage of metal fingers. He quickly straightened and opened his hands, his optics flickering furiously as he cycled through a gamut of scanner probes, all attuned to the small person resting in a daze on his palm.

"Samuel, are you damaged?" The young man did not answer, staring up at the ceiling with an expression of dizzy surprise, and Ratchet felt worry begin to lace threads of poison through his mind. "Sam! Respond!"

A moment later, the young man blinked and obediently focused his eyes on Ratchet's face. He pushed up heavily on one elbow and flapped his hand, as if batting at an invisible swarm of insects. "Enough with the scans, already! They tickle."

Ratchet frowned and tipped his palm over the exam table, dropping Sam on his butt with a startled yelp. Venting an explosion of air, all but incoherent with rage, he waved a fingertip as large as a bowling ball an inch from Sam's nose. As the human went cross-eyed trying to focus on the digit, Ratchet finally ground out, "You- you- _stupid_ boy! What the slag did you think you were doing?"

"Research?" Sam ventured.

With an audible squeal of compressing dental plates, Ratchet curled his finger and flicked Sam on the side of the head. Under ordinary circumstances, the blow would have caved in his temple like a grape, but now the portable shield simply flickered into the visible spectrum, briefly washing Sam's vision in blue. The bleed through from the force field was too light to be painful, as if he had been slapped by a very small and angry child.

"Do you understand the meaning of the word prototype?" Ratchet asked, in his best 'talking to morons' voice. "It means the first of a new model. As in untried. As in _it might not work._ You could have broken your neck, and _I do not want_ your carcass staining my med bay's shiny new deck plating."

He planted his hands on either side of the object of his wrath, sending vibrations through the table and up Sam's legs like a micro quake. The lenses in Ratchet's eyes expanded and contracted with a barely audible whirr, before focusing on Sam's face with an expression of ominous intent. "I think Bumblebee should know about this little stunt."

His reaction was everything Ratchet could have hoped, for Sam recoiled as if menaced by a pit viper. "God, no! He still hasn't gotten over his 'Sam's-hurt-must-hover' stage. If you tell him now, he'll snap like a twig and weld all the doors and windows in my house shut. I'll spend the rest of my life being fed and watered through the vents like a hamster. A hamster, Ratchet!" In a wholly human display of overdramatics, Sam fell to his knees and clasped his hands together in entreaty. "Have mercy! I'll be good."

The corner of Ratchet's mouth twitched in a hint of a smile, before he straightened and removed his hands from the table. "I'm glad to hear it. See that you do."

"Yessir."

Slightly mollified, Ratchet let his curiosity come to the forefront, staring critically at the clunky shoulder harness. "So how did it feel when you landed?"

"Weird. For about half a second, it felt like something was pressing down on every part of my skin, like a full body hug. It didn't hurt, but it kinda knocked the breath out of me." Sam shifted into a more comfortable sitting position and fiddled with one of the chest straps, which had begun to fray at the end. "It was fun, though. Like bungee jumping, but a hundred times cooler."

In a gesture he had seen Mikaela use many times before, Ratchet pinched the bridge of his nose and groaned. "Primus forbid the Twins show up in your lifetime. You wouldn't last a week."

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_**AN:**__ There was really no point to this fic, except that I wanted Ratchet and Sam to interact a little. I also wanted Ratchet to whack a human without killing him, and to find some way to make said human less squishable. And even though I know very little about the theoretical application of force fields, I wanted to see if I could make the subject sound plausible. I'm sure there's a Physics student out there who has read this fic and is now laughing at me. :-)_

_If you want the damage figures in regard to joules, then here they are: A punch is approx. 82.32 joules. A tap from Ratchet's finger is approx. 402.2 joules. A 30 caliber bullet is approx. 49,421.4 joules. A fall at terminal velocity is approx. 119,743.83 joules. A Prowl-related car crash at fifty m.p.h. is approx. 412,106.1 joules. A Prime hit and run at fifty m.p.h. is approx. 9,063,186.4 joules. An AIM 120 missile strike is approx. 140,817,773.44 joules. _


End file.
